Logic analyzers are well-known devices that are connected to the digital bus of a system to read addressed information on the bus and provide a digital indication of either or both the address and the information associated with the address. For instance, in a digital system, a system using a microprocessor, various diagnostic system tests can be performed with a logic analyzer intercepting the flow of information within the system.
But generally speaking, currently available logic analyzers are expensive, especially those that use an oscilloscope to display the encoded information. With these, the user must convert the displayed code to know what the encoded data is. Though, sometimes in more expensive analyzers the code is converted and displayed on the screen.
But, in many test applications such sophisticated equipment is not really appropriate, and not simply because of cost, but also because the equipment does not provide the most useful--practical--information for "diagnostic" testing. The field of elevator maintenance offers good examples. In a microprocessor-controlled elevator, encoded digital information may be used very effectively for diagnostic testing, for instance, actual and theoretical operational tests. In some tests, the actual information on car location and car velocity can be used to create waveforms or graphs showing actual car motion. This would yield a very effective diagnostic field test. State-of-the-art logic analyzers, however, could not be used to perform this type of test--at least not conveniently or inexpensively.
Sometimes, for some tests only a small portion of that digital information is needed. The status of a single device, for example, a relay in an elevator, may be indicated in a digital word consisting simply of a device identifying address and status bit (indicating the status, e.g. ON/OFF, of the device). In performing a diagnostic test, a service technician may simply need to see a light or meter go on or off, to observe the operation of the device.
In short, there, the need exists for a small, compact, inexpensive analog logic analyzer.